This invention relates generally to semiconductor circuits, and more particularly to an improved current mirror circuit using metal-oxide-semiconductor (MOS) field-effect transistors.
A current mirror is a current-controlled current source wherein the current output is constant for a given current input. Typical applications of this circuit include bandgap voltage references, operational amplifiers and comparators. In complementary MOS (CMOS) applications using this circuit high impedance stages are desirable for high gain, low offset, and high power supply rejection ratio. One method of meeting these requirements is to use stages with cascoded outputs. A typical circuit having cascoded outputs requires a voltage equal to twice the gate to source voltage, or 2 V.sub.GS, on the input and a voltage equal to the difference between this voltage and the threshold voltage, or (2 V.sub.GS -V.sub.T), on the output for proper operation. However, this prevents the output from directly driving a subsequent stage requiring only one V.sub.GS on its input unless a level translating circuit is included.